Paper manufacture



J.- TRAQUAIR PAPER MANUFACTURE 7 Filed April 27, 1928 INVENTOR.

7- /la.& ATTORNEYS.

Patented Feb. 2, 1932 rrso STATES PATENT OFFICE I JOHN TRAQUAIR, or GHILLICOTHE, 01110, ASSIGNOR ro THE MEAD coarom'rron, or

DAYTON, 0310, A coaromrron or 01110 PAPER MANUFACTURE Application filed April 27,1928. Serial No. 273,241.

This invention relates to the manufacture of paper .and the like from cellulose-containing materials, and particularly to the pre aration of pulp to be used in such manu acture.

One of the principal objects of the invention is to provide a method of treating fibrous materials to produce a superior pulp productwhich may be formed into a paper havw .ing strength, color and other characteristics superior to the corresponding characteristics in paper formed from the same fibrous materials in other previously known ways. a, Another object of the invention is to pro- 1 7' vide a method of chlorinating and bleaching fibrous materials to produce a pulp product which may be formed into a superior paper having unusual strength, purity and color.

\ Still another object of this invention is to provide a method of chlorinating and blaaching fibrous materials, which is continuous in operation, which is highly effective and easily grammatic illustration of a preferred. form of apparatus constructed for carrying out the method of this-invention.

In the manufacture of pulp from fibrous materials. it is the universal practice to sub- 40 ject the fibrous material to a chemical treatment which loosens and removes to a more or less degree the lignins and other incr-ustants which hold the fibers bound together, so that the fibers may be separated, after which the separate fibers, or pulp stock, is ordinarily subjected to a bleaching action to increase the whiteness of the fibers to the desired degreedepending on the'field of utilization of 'the finished pulp stock. Because of the limso itations heretofore imposed on this bleaching action it has been necessary, under old methods of pulping, to sacrifice either quantity of yield (with reference to the total quantity of fibrous material utilized), or quality of finished pulp.

This has been especially true with respect to certain types offibrous materials, such as straw, flax, fibrous grasses, and the like. In such materials an inordinately large proportion of the fibrous material must be'destroyed during the preliminarydefibering, if the hard fiber bundles or shives, for example,

' are to be sufiiciently defibered to permit of securing a final pulp of satisfactory whiteness using the bleaching methods heretofore known. Also with respect to certain hard woods, such as oak, chestnut, gum veneer c0re's,-etc., for further example, the same thing has been true, and even with drastic defiberlng treatments it hasnot been commercially feasible to secure a suitable pulp from such woods.

The' present invention provides a method of treatlng fibrous materials which have been given a preliminary defibering treatment so as to more or less completely separate the fibers thereof, whereby desired quality of pulp is secured without undue sacrifice'in quantity. Particularly is this true with materials such as straw, in which the preliminary cook as ordinarily used fails to com pletely defiber the shives, etc. In carrying out this method suitably defiberedmaterial is subjected to successive treatments to produce pulp of unusual and superior strength and colorcharacteristics, these treatments being hereinafter termed halogenation treatments for purposes of description. V

The more or less defibered material is first subjected to the action of a lialogenating agent such as a 'chlorinating agent in a manher to prevent a temperature, rise ofthe mass undergoing chlorination such asto deleteriously aflect the strength of the fibers. This may be accomplished by diluting the fibrous stock to a low consistency. In such case the water in which the fibers are -suspendedapparently serves as a heat-absorbing medium to avoid an objectionable temperature rise with injury to fibers. The water also serves I ing chambers.

to dilute the hydrochloric acid formed in thg comparatively short time as the mass flows along. The amount of chlorinating agent is preferably controlled to be as much as will be readily taken up by the fibers in this short treating period, while insuring substantially complete reaction. This initial reaction is rapid, and it has been'ascertained that the reaction of about 85% of the chlorine required for complete chlorination of a given fibrous mass goes to substantial completion in about fifteen to twenty minutes. Generally the addition of about to 95% ofthe chlorine needed for complete chlorination in the first stage with a treating time of about half an hour gives very satisfactory results. Various halogenating agents may be used for this first stage, chlorine bein preferred due to the ease of control, and efiectiveness and rapidity of the reaction. However, the use of ordinary bleach or other calcium compounds at this point is found objectionable due to the formation of insoluble calcium re action compounds in the pulp which arenot readily Washed out inthe subsequent alkali washing treatments. The chlorine may be added at a controlled rate in the form of chlorine Water. Or the chlorine water solution may be added to the water in which the fibers are suspended to provide the desired consistency. Or chlorine gas may he introduced at a controlled rate directly into the fibrous stream which has previously been made down to the desired low consistency.

After this initial haloge nation, it is found a that the fibers may be subjected to a strong or drastic halogenating reaction with chlorine gas or bromine at high density or consistency without objectionable results. There will be no deleterious temperature rise or'deleterious acid formation under such'secondary conditions, and the strength of thefibers is main- I tained and other high quality characteristics are secured. After such first-stage treatment the fibrous mass is washed preferably with an alkali treatment, and is then thickened and rendered permeable to gas, and is then sub jected to the action of a gaseous halogenating agent, such as chlorine gas, whereby the chlorination is completed. In this phase of.

chamber may be so more drastic action, in which a high chlorine concentration is eflective in the fibrous mass, the chlorine gas reacts with the more resistant ligne ous matter with consequent resolution of the shives or other undefibered material. During such reaction the ligneous, and other material in the shives, or the like, is apparently changed by the action of the chlorine gas into compounds which may be readily washed out with alkaline solutions, or the like; or which, even if not thus capable of being washed out, are of such character as to color, etc.,- as to be subsequently unobjectionable and inefiective to lower the quality char-' acteristics of the resulting pulp. Very satisfactory results are secured in this phase with consistencies of substantially 15% or higher. The fibrous stock at such chamber having an atmosphere of chlorine gas, in such wise that the chlorine gas thoroughly permeates the mass of fibers and effects intimate contact therewith. In practice it is desirable to secure continuous treatment throughout theentire cl'ilorinating process, and for this the rate of travel through the controlled as to elfect continuous treatment of the material result- "mg from the treatment in the first stage. Generally a treating period of fifteen to thirty minutes in this second stage is satisfactory, although a longer period may be used. The chlorinated pulp resulting is then steeped in alkali to dissolve out the reaction products of the chlorination," and washed. This pulp may then be additionally bleached with 'a small amount of hypochlorite to secure a high white. The alkali steeping, washing and bleaching are preferably continuous whereby the entire process may be continuously carried out with accurate control and a minimum of attention.

Referring to the drawing, a pump is indicated at 10 for pumping the defibered material or washed brown stock comingfrom the digesters and wash pans or other pulping equipment, (not shown), through the pipe 11 to the chlorinating apparatus. The fibrous material at this point is diluted to a low consistency such that objectionable temperature rise in the initial chlorination is prevented. A controlled supply of chlorinating agent such as chlorine water or chlorine gas, is i%troduced.into the stream of fibrous material trol valve 13. The fibrous mass and chlorin-' ating agent pass together into. a mixer 14 which comprises a length of pipe having a spiral baflle 15 therein to create turbulence in the flowing stock stream to mix the chlorinating agent with the mass, and from the mixer pass into a chlorinating tank or chamber16. I r' j The chlorinating tank 16 is constructed'of y pipe 12, which has a con- 7 high density is preferably passed continuously through a acid-proof material such as tile or concrete ca and also "drit and is divided intd a plurality of connected chambers or compartments, re resented inthe drawing by two chambers 1 and 18 divided. by a central partition 19 terminating short of the bottom of the tank. The mixed 23 having an interior ribbon conveyor or 20 spiral 24 and spray pipes 25 for spraying wash water upon the stock. The stock feeds into the interior of one end of the rotary drum, and iscarried continuously through,

- being washed by the sprays and discharged 25 from the other end, a part of the water therein draining through the perforated drum into a receiving tank 26 so that the stock generally discharges from the washer at a consistency of about to.12%. The 30 short timeof treatment in the chlorination chamber coupled with the fact that the free acid.formed in' the reaction is washed out immediately after chlorination further serves to preventinjury' to the fibers. An addi- 35 tional spray pipe 27 is preferably provided to directan alkaline; solution upon the washed fibers to neutralize any acid or free chlorine remaining in the fibrous] mass thus avoiding the necessity for further acid-proof 40 apparatus, aswell as assisting in dissolving.

out reaction products of the chlorination; If desired, an alkaline steeping in addition to the washing may be fgivenat this point, this beingfoundladvantageous'in the case of eufibrous stock which is less defibered. r

The discharge 28 from the worm washer feeds to-a furtherthickening device where the stock is dewatered to a consistency of substantially or higlher, preferably co to 30%, to'-renderthe pu p; readily permeable This is preferably a continuous cento 'gas 7 tri ugal'machine. of" the type'shown in the patent to Laughlin,-.l,6j5 5-,426, dated January 10,11928. This machine comprises an inner distributing. rotor- 30 having a spiral flange 31,1tl1e rotor being keyed to .a shaft 32 driven by ,amotor, 33, and ,a's'econd rotor or perforated filtering screen-"34carried by a sleeve :35rot ijbly mounted upon shaft 32 l from motor 33 through suitable gearing-atf-a speed-which is preferably f slightly less than the speed of'the rotor 30.

-Thefouter screenis-surrounded by a stationv ary. annular trough 36 forming an enclosing casing. The 'discharge27 continuously feeds 'ing from the tower the stock into the space between the inner rotor and the outer filtering screen, where it is carried through the machine by the spiral flange 31 while being subjected to such centrifugal force as to cause a portion of the retained water in the pulp to pass through the filtering screen 34 into the trough 36, from where the filtrate is removed ,by a pipe 36'. Other well-known types of continuous thickeners may be used for this purpose, such as rotary vacuum filters or cylindrical thickeners with pressure rolls to regulate the water content of the stock.

The dewatered stock discharged from the centrifugal machine is fed by a chute 37 to a supply trough 38 from where it is scooped by an endless bucket elevator 39 and fed into. a treating tower 40 constructed of acid and chlorine proof material, where the second stage of the chlorination treatment is effected. Preferably a chlorinating tower such as that described in the a plication of John Traquair and Francis Rawling, Serial No. 273,242, filed of even date herewith, is used. As shown diagrammatically herein, the elevator 39 discharges into a hopper 42 which feeds into a screw conveyor 43 having 'an opening 44 on the lower side thereof opposite the open upper end 45-of the tower 40. Stock feeds through the opening '44 into the upper "end of the tower 40 as needed to maintain the. tower full of'stock, the surplus stock handled by the screw conveyor 43 being discharged. at the end 46 and returned to the source of supply. The tower 40 is provided with an inlet 48 for a controlled supply of vchlorine gas,.and controlled outlets 49and 50 for the discharge of gas. The gas dischargwhich contains some free chlorine, is preferably passed to recovery apparatus,- (not shown) such asa water absorp-, tion system wherechlorine water is formed which may be used in the first-stage chlorination. Water or other slushing liquid is introduced adjacent the base of the tower at 51 to dilute and slush out the stock through the water-sealed bottom 52 of the tower into a trough 53, the stock passing from the upper a continuous travel of dewatered stock through a'controlled and maintained atmosphere of chlorine gas. The stock may be fed from the trough 53 to a storage tank, or it may be passed di-" shown, the stock discharges'througli a pipe 56 rectly to further treating apparatus.

into a solvent tank 57 Here it is mixedwith a controlled quantity of alkali, continuously supplied from a'pipe 58. The tank 57 is constructed to effect a continuous and uniform treatment of the material passing therethrough, and to secure a thorough mixing of the fibers with the solvent alkali. For this purposefthe tank is provided with a plurality of staggered baffles 59 which provide a circuitous flow of the material from the inlet 8 60 to the discharge 61 connected to the suction side 'of a pump 62. The first compartment of the tank 57 is preferably provided with suitable agitating mechanism such as a driven shaft 65 having a plurality of rotarya pipe to a continuous filter mechanism the suction compartments.

which serves to wash and thicken the treated material. This filtering mechanism may be a conventional rotary vacuum filter, such as an Oliver filter. This comprises a perforated rotary screen 72 divided into compartments of definite suction areas. The screen dips into the stock confined within a tank 73. The stock from pipe 7 0 together with sufficient water to make down to a consistency of about 1% is discharged nto tank 73, and suction within the compartments of the screen causes the. fibrous material to accumulate on the surface of the screen as the water passes into As the screen rotates carrying the filtered fibrous material above the liquid level within the tank, sprays of wash water or dilute alkali are directed upon the material from spray pipes 74. The dissolved reaction products of the chlorination and the excess alkaline liquor are thus washed out of the stock, while controlled suction draws liquor from the fibrous layer. As the filter continues to rotate, the material which has thus been washed and thickened arrives at an area which is not subject to suetion, and at this point a flexible scraper member 75 scrapes the material from the filter into a chute 76 which discharges into the first tank 80 of a bleacher which is preferably of the continuous type. The alkaline liquor and wash water drawn by suction into the interior of the rotary screen 72 are discharged through acentral pipe 77. A portion of this alkaline. liquor may be supplied to the spray pipe 27 of the worm washer.

Any suitable construction of continuous bleacher may be used. As shown, three con-' nected tanks 80, 81 and 82, each having a rotary shaft 83 with agitating arms 84, are provided. The tanks are arranged at successively lower elevations. and the bottom of a preceding tank is connected to the upper end of a succeeding tank by a pipe connection 85. Each connection 85 has its highest point located below the level of the stock in the preceding tank, whereby a head is effective to secure a How through. the pipe. The capacity of the tanks is such as to insure sufficient time for the completion of the final bleaching action during the time the material flows through the connected bleaching tanks. A suitable bleaching agent, such as bleach liquor, sodium hypochlorite, or chlorine water is continuously added by pipe 86. Due to the effective chlorinating action, the quantity of bleach required is very materially reduced, approximately 1%to 3% of bleach liquor on the dry weight of the pulp being suflicient to produce a pulp having a high white color. The bleached pulp continuously discharging from the last tank 82 through pipe 88 is forced by a pump 89 to a second rotary vacuum filter 90 similar to the filter '71 where the pulp is washed and thickened. The treated pulp is then discharged through chute 91 into a stock chest 92 where it is stored for further treatment or for use.

The following is a typical example of a chlorinating treatment carried out in accord-- ance with this invention. For the first-stage chlorination, chlorine water containing approximately 80% to 90% ,of the chlorine required for complete chlorination of the pulp is used. The chlorine is added to the stock in the form of a solution in water containing approximately 2% to .49 0 chlorine, or is added directly as chlorine gas. In the former case the raw fibrous material is made down to a consistency of about 4% to 6%, the addition of the chlorine {water bringing the consistency to about 1% to 4%. In the latter case the consistency of the material is made down initially to about 2% or even less. The rate of flow through the chlorination chamber is controlled to give a treating time of about half an hour. The stock is then given an alkaline treatment and Washing, andafter thickening to about 20% to 30% consistency is then fed to the chlorinating tower where it is subjected to the second-stage chlorina- '1 tion by passing through a maintained layer of chlorine gas for about fifteen to thirty minutes. Both stages of the chlorination are carried on at ordinary room temperatures.

The chlorinated stock is then'introduced into the alkali solvent tank with a sufiicient quan tity of cold .1% NaOH solution to render the mass distinctly alkaline, and is agitated and to 5% and to provide about 3% bleach liquor on the dry weight of the pulp. The flow of stock through the bleacherv is controlled to provide a treating time of about one hour or more. A preliminary high *density bleach may be given, if desired, before the stock is diluted to about 4% to 5%. The bleached pulp is then washed and thickened and fibers, thickening dropped to a stock chest.

While the method herein described, and the form of apparatus for carrying this method into efiect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and .that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. The method in the pulping of fibrous material which has beentreated to separate its fibers, or defibered; which comprises diluting the defibered material to low consistency, subjecting the diluted material to the action of a halogenating agent, the consistency of said diluted material being controlled to prevent during halogenation a temperature rise of said diluted mass sufficie nt to deleteriously affect the strength of the fibers, then raising the consistency of said halogenated material, and subjecting said material of higher consistency. to the action of a halogenating agent.

2. The method in the pulping of fibrous material, which comprises diluting defibered material to a consistency of less than 5%, subjecting the diluted material to the action of a halo enating a cut, the consistency of the dilute material eing controlled to prevent during the halogenation a temperature'rise of said diluted mass-sufic'ient to deleterously,

afiect the strength of the fibers, then dewatering the material to a consistency of substantially 15% or higher, and subjecting said dewatered material to the action of a halogenating agent in high concentration.

3. The method in the pulping of fibrous material, which comprises diluting defibered.

material to low consistency, treating said diluted material with a halogen-containing solution, the consistency of said diluted material being controlled to prevent during the treatment a temperature rise of the mass sufficient to deleteriously aflfect the strength of the said treated material to render it permea e to gas, and then treating said thickened material with a gaseous halogen.

4. The method in the pulping of fibrous material, which comprises diluting defibered material to low consistency, chlorinating-said diluted material with chlorine water, the consistency of said material being controlled to' prevent during the chlorination a temperature rise of said mass sufiicient to deleteriously affect the strength of the fibers, raising the consistency of. said chlorinated material to \rpnder it. permeable to gas, and then chlorinatingitm thickened material withchlorine gas.

5. The method in the pulping of fibrous material, which comprisekfirst treating .fibrous material with a halogenating agent and concomitantly limiting. the temperature rise of the mass as a result of such treatment to prevent deleteriously affecting the strength of the fibers, washing and thickening the and thickening the chlorinated material, and

then completing the chlorination ofthe Washed and thickened'material with chlorine gas. 7. Themethod in the pulping of fibrous material, which comprises first treating fibrous material with a halogenating agent and concomitantly limiting the temperature rise of the mass as a result of such treatment to prevent deleteriously affecting the strength l v of the fibers, washing and thickening the treated material, treating the washed and thickened material with a gaseous halogenat ing agent, and treating the resultant mass with an alkaline solvent to dissolve out the reaction products of the halogenation.

8. The method in he pulping of fibrous material, which comp ises first chlorinating fibrous material with a chlorinating agent and concomitantly limiting the temperature rise of the mass as a result of such chlorination to prevent deleteriously affecting the strength of the fibers, rendering said chlorinated ma terial alkaline and washing without substantial delay, raising the consistency of said washed material toirender it permeable to gas, chlorinating the thickened material with a gaseous chlorinating agent in high concentration, and treating the resultant material with an alkaline solvent and Washin 9. The method in the pulping 0% fibrous material, which comprises first chlorinating fibrous material with a chlorinating agent and concomitantly limiting the te .iperature rise of the mass as a result of such chlorination to prevent deleteriously affecting the strength of the fibers, washing and then raiswashed material to render it permeable to gas, chlorinating the thickened material with chlorine gas, treating the resultant material with alkali and washing, and then bleaching 3 said treated material.

10. The method in the pulping of fibrous material, which comprises diluting fibrous material to a consistency. as less than"5%,

chlorinating the diluted material with chlo rine water, the consistency otthe mass being the consistency of said chlorinated and into said flowing stream whereby halogenation of the material takes place as the mass flows along, continuously raising the consis-' .tency of the treated material to render it permeable to gas, and continuously treating said material Qfhigher consistency with a halogenating agent in high concentration.

12. The method in the pulping of fibrous material, which comprises diluting defibered -material to low consistency, feeding the di luted material in a continuously flowing stream, introducing a chlorinating agent into said flowing stream whereby chlorination of the material takes place as the mass flows along, the consistency of said massbeing controlled to prevent during the chlorination a temperature rise of said mass sufficient to del-' eteriously affect the strength of the fibers, cont nuously raising the consistency of the chlorinated material tofrender it permeable to gas, and continuously feeding said material of higher consistency through an atmos phere of chlorine gas. v

13. ,The method in the pulping of fibrous material, which comprises first treating fibrous material with a halogenating agent and concomitantlylimiting the temperature rise. of the mass as aresult of such treatmeet to prevent deleteriously affecting the strength of the fibers, treating the halogenated material with alkaline solvent and washing, thickening the washed material, treating thethick-ened material with a halogenating agent, and then treating the material with an alkaline solvent and washing.

14, The method in the pulping of fibrous material, which comprises diluting defibered material to low consistency, feeding the diluted material in a continuously flowing stream, introducing a halogenating agent into said flowing stream whereby halogenation of the material takes 'place .as the mass flows along, continuously treating the resultant material with analkaline solvent and washing, continuously thickening the washed material torender it permeable to gas, con- '601 tinuously treating the thickened material with a gaseoushalogenating agent, and then treating the material continuously with' an alkaline solvent and'washing'.

15-. The method in the pulping of fibrous material, which comprises diluting incompletelydigested fibrous material to low consistency, feeding the diluted material in a continuously flowing stream, introducing a halogenating agent into the flowing stream whereby reaction of the halogenating agent with the fibrous material takes place as the mass flows along, thickening the halogenated material, treating the thickened material and with an alkaline solvent and washin then bleaching the Washed material.

16. The method in the pulping of fibrous material, whichcomprises diluting incompletely digested fibrous material to low con sistency, feeding the diluted material ina continuously flowing stream, introducing a halogenating agent into the flowing stream whereby reaction of the halogenating agent with the fibrous material takes place as the mass flows along, thickening the halogenated material to render it permeable to gas, passing the thickened material by gravity through. an atmosphere of chlorine gas, removing the treated material from the chlorine atmosphere, and then treating the removed material with an alkaline solvent and washing.

17. The method in the pulping of fibrous material, Whichcomprises diluting incompletely di ested fibrous material to low consistency, ceding the diluted material in a continuously flowing stream, introducing a halogenating agent into the flowing stream whereby reaction of the halogenating-agent with the fibrous material takes place as the mass'flows along, treating the resultant material with an alkaline solvent and washing, thickening the washed material to a consistency of substantially 15% or higher,passing the thickened material by gravity downwardly through a maintained column of chlorine gas, removing the treated material from the maintained column and then treating the removed'material wit-h an alkaline solvent.

In testimony whereof I hereto aflix my signature. i v

' JOHN TRAQUAIR. 

